Ever increasing complexity, power consumption, computing prowess, and functionality of modern microelectronic devices have dramatically increased the demands on the integrated circuits and semiconductor structures incorporated within these devices. Indeed, modern microelectronic devices having advanced semiconductor elements, such as cellular phones and portable music players, generally must dissipate a great amount of heat during operation in order to remain within acceptable operating parameters. As device size decreases, it becomes increasingly important to adequately dissipate heat from the device elements. These microelectronic devices typically incorporate at least one thermal interface device, such as a heat sink, in order to absorb and dissipate heat, thereby reducing the thermal load on the device elements.
Common device elements often include ceramic components made of silicon carbide, aluminum oxide, aluminum nitride, gallium nitride, gallium arsenide, or beryllium oxide. These elements often include a heat sink in order to dissipate heat generated during operation. As semiconductor and integrated circuit complexity increases, while physical size decreases, heat generated by these at least now state-of-the-art microelectronic device elements will also increase.
Conventional heat sinks are commonly fabricated from metals such as aluminum, copper, molybdenum, or tungsten. Metals such as copper or aluminum, while often having high thermal conductivity, also have undesirably high coefficients of thermal expansion. Such high coefficients of thermal expansion often mismatch with the underlying, or associated, device element's coefficient of thermal expansion which can lead to increased mechanical stress while under static or cyclic thermal loading. The differential expansion of the heat sink relative to the underlying, or associated, element can cause cracking, or other failure. Some metals such as tungsten and molybdenum, while having relatively low coefficients of thermal expansion, unfortunately exhibit lower thermal conductivity and higher density than desired and may not be suitable for certain thermal management applications. Moreover, these traditional heat sink materials are simply proving to be insufficient when challenged with ever increasing electronic device power densities.
Metal matrix composites, generally providing a ceramic-based macrostructure having void volume fraction filled by a molten metal, have been developed as an alternative to metal heat sinks. Still further, these composites may also typically include inorganic fibers as an inorganic filler material to be additionally incorporated within the void volume fraction. These metal matrix composites, nonetheless, also suffer drawbacks. Filler incorporation, for example, may lead to non-uniform distribution due to simple displacement and/or wetting difficulties. It is often, accordingly, difficult to properly manage incorporation and distribution of the filler phase to obtain target properties for the composite. Conventional metal matrix composites also offer limited ability to match the coefficients of thermal expansion with underlying device elements and can also be difficult to fabricate to appropriate size. These conventional metal matrix composites further lack sufficient thermal conductivity to address the growing need for higher levels of thermal dissipation.
Ever-increasing power densities in microelectronic devices have resulted in the need for composite materials to provide improved thermal dissipation for microelectronic device elements. Accordingly, there is a need in the art for lightweight materials having higher thermal conductivities than that offered by traditional materials for higher thermal dissipation while also providing suitable coefficients of thermal expansion that minimize thermal mismatch with associated device elements. There is a further need for methods of producing such composite materials having macrostructure architectures that provide for improved infiltrant incorporation while providing for improved balance between thermal conductivity and thermal expansion properties.